Reduction of the spectral linewidth of semiconductor lasers with quantum wire effects—Spectral properties of GaAlAs double heterostructure lasers in high magnetic fields

The spectral linewidth of a GaAlAs double heterostructure laser placed in a high magnetic field is measured at 190 K. It is found that the power-dependent spectral linewidth is reduced by a factor of 0.6 in a magnetic field of 19 T. This reduction is believed to result mainly from the reduction of the linewidth enhancement factor alpha due to a quasi-one-dimensional electronic system formed by the high magnetic field (i.e., by quantum wire effects)

Parallel matrix inversion techniques

In this paper, we present techniques for inverting sparse, symmetric and positive definite matrices on parallel and distributed computers. We propose two algorithms, one for SIMD implementation and the other for MIMD implementation. These algorithms are modified versions of Gaussian elimination and they take into account the sparseness of the matrix. Our algorithms perform better than the general parallel Gaussian elimination algorithm. In order to demonstrate the usefulness of our technique, we implemented the snake problem using our sparse matrix algorithm. Our studies reveal that the proposed sparse matrix inversion algorithm significantly reduces the time taken for obtaining the solution of the snake problem. In this paper, we present the results of our experimental work

Enhanced modulation bandwidth of GaAlAs double heterostructure lasers in high magnetic fields: Dynamic response with quantum wire effects

The modulation bandwidth of GaAlAs double heterostructure (DH) lasers in high magnetic fields is measured. We found that the modulation bandwidth is enhanced by 1.4× with a magnetic field of 20 T. This improvement is believed to result from the increase of the differential gain due to two-dimensional carrier confinement effects in the high magnetic field (quantum wire effects). A comparison of the experimental results with a theoretical analysis indicates that the intraband relaxation time tauin of the measured DH laser in the range of 0.1 to 0.2 ps

Large-signal dynamics of an ultrafast semiconductor laser at digital modulation rates approaching 10 Gbit/s

High-fidelity pseudorandom digital modulation at 8.2 Gbit/s of an ultrahigh speed semiconductor laser is demonstrated. Studies using simple but representative pulse patterns at 10 Gbit/s give insights into the maximum digital modulation rate attainable from a given laser, as well as relations between large-signal digital performance and small-signal analog response

Intermodulation distortion in a directly modulated semiconductor injection laser

A most important quantity in high-frequency analog transmission is the intermodulation distortion product. Experimental studies of the third order intermodulation distortion products in the modulation response of high-speed semiconductor lasers give very low values (< −60 dB) at low frequencies, an increase at a rate of 40 dB/dec as the modulation frequency is increased, and a leveling off at one-half of the relaxation oscillation resonance frequency. These experimental results can be well explained by a theory based on a perturbative analysis of laser dynamics

Microwave Optical Link In The Frequency Range Of 10-18 Gigahertz By Direct Modulation Of Injection Laser Diode

It is demonstrated that an ultra-high speed window buried heterostructure GaAlAs laser fabricated on semi-insulating substrate can be used as narrow band signal transmitters in the Ku-band frequency range (12-20GHz). The modulation efficiency can be increased over a limited bandwidth by a weak optical feedback. A stronger optical feedback enables one to actively mode-lock the laser diode at a very high repetition rate up to 17.5GHz, producing pulses of = 12ps long

Analog, Digital And Short Pulse Modulation Of Ultrafast Gallium Aluminum Arsenide Semiconductor Lasers

Semiconductor lasers are potentially devices of great importance for optical transmission as well as short pulse generation for various sampling, characteration and dispersion measurements. Since semiconductor lasers are currently driven devices, it is relatively easy to modulate the optical output and to generate short pulses, on the order of 10 ps long, by directly modulating the injection current into the laser. This paper will present some recent developments in injection lasers which are capable of being analog or digitally modulated at rates up to 10 GHz, as well as generating short optical pulses at repetition rates from several hundred megahertz to tens of gigahertz

Self-sustained picosecond pulse generation in a GaAlAs laser at an electrically tunable repetition rate by optoelectronic feedback

We demonstrate that applying optoelectronic feedback to a high-speed, self-pulsing semiconductor laser is an effective and practical means of generating picosecond optical pulses (~10–20 ps) at a very high repetition rate, between 1 to 5 GHz, which can be electrically tuned. The optical pulses are very stable both on a short term basis with a frequency stability of one part in 10^5, and on the long term basis as a result of the absence of critical optical alignment. This laser system is potentially very useful in high-speed electro-optic signal processing, optical multiplexing, or laser ranging